Building block



FIG. 1 is an perspective top view showing the top, front and right side of the building block of this invention.

FIG. 2 is an perspective bottom view showing the bottom, back and left side of the building block of this invention.

FIG. 3 is a side elevational view thereof;

FIG. 4 is a top plan view thereof; and

FIG. 5 is a top plan view of the right side of the block shown in FIG. 4. 

The ornamental design for a building block, as shown and described. 